Process of photo-printing



Patented A r. 9,1935;

f UN l TED STATE 1,997,501 rnoonss 0F PHOTO-PRINTING Vladimir C. Akintievsky, New York, N. Y

' No Drawing. Application March 9, 1932,

Serial No. sevsiz l8 il'jlaims.

cipally for the from tracings by the action of light,

purpose of reproducing drawings and in which azo dyes are also formed upon a-sensitized carrier;

In view of the differences between my process and the diazo-type tinctive name photo-printing.

process, I have adopted as a disfor my process, the title diazo Diazo compounds may be divided into two general classes, the first class comprising those diazo compounds that display the characteristic property of couplin g with coupling components such as amines, phenols and amido-phenols, and. the second class comprising those diazo compounds that do not show this characteristic reaction.

Diazo compoun syn-diazo comp ds of the first class may be termed ounds or iso-diazo compounds, and

those of the second class may be termed antidiazo compounds or normal diazo compounds, 1-

shall use these terms herein in the foregoing As is well known, azo dyes may be formed by coupling two components under suitable conditions, one component being a syn-diazo compound, and the other being a so'called azo dye-forming coupling component, or,

more briefly, a coupling component, principally an aminaphenol or amido-phencl.

Diazo compounds may be decomposed by light to form phenolic bodies, which are of course not capable of forming azo dyes with coupling components. This type process.

type process, paper is coated with a light-sensitive. anti-diazo compound alone, and then exposed unreaction is the basis of the diazo In one embodiment of the diazoder a negative or tracing, the diazo compound being decomposed where the light strikes. The

sensitized pape r after exposure is developed with an alkaline solution of a coupling component. The

alkali converts the anti-diazo compound into a syn-diazo compound, which then couples with the coupling component so that an azo dyestufi is formed on the unexposed portions of the paper.

iyp'e process, but in all'of them thefundamental reaction is the conversion of a light-sensitive diazo compound into light.

a phenolic body bythe action of (ill. 95-6) Diazo photo-printing, on the other hand, is based on the reactions exhibited by diazo sulphites and certain analogous diazo compounds. "The diazo sulphites, when properly prepared from other diazo compounds in the absence of strong actinic light, do not display the characteristic property of coupling with coupling components and hence belong to the class of anti-diazo compounds. Upon exposure to strong actinic light under suitable conditions, however, a syn-diazo compound is formed.

In the diazo photo-printing process, therefore,

the carrier may be sensitized in the absence of strong .actinic light with a mixture of a coupling component and alight-sensitive diazo sulphite, and the sensitized carriermay then be exposed to, light, whereupon the diazo sulphite is decomposed with the formation of a syn-diazo compound which proceeds to couple with the coupling component toform an azo dye directly on the portions of the carrier exposed to the light.

The discovery that certain diazo sulphites possess the property of coupling with dye-forming components only after exposure to light, was made by Adolf Feer in Germany and disclosed by him in German Patent No. 53,455, published Au- 5 PATENT OFFICE gust 19, 1890. Peer neglected to give any description of the preparation of his sulphites, but a general method for the preparation of these compounds was given by Lumiere in a paper published in the Bulletin Soc. Francaise de Photographic for 1896, at page 195. Lumieres general method 7 is as follows: To a neutral diazo compound, in aqueous solution at 10 (3., is slowly added a cold,

concentrated aqueous solution of sodium sulphite in excess of molecular proportions, preferably two molecules of sodium sulphite to one molecule of diazo compound. The mixture at first displays the property of coupling with coupling components to form azo dyes, but rapidly loses this property. The reaction product may be precipitated by salting out with sodium chloride, filtered ofi, and purified, if desired, by redissolving, filtering the solution and-reprecipitating. Upon exposure to strong actinic light, the reaction product shows the characteristic syn-diazo reaction of coupling with dye-forming components to form azo dyes.

Fe'er considered the compoundformed to be a diazo sulphonate having the general structural formula RN=NSO3Na, and Lumiere followed There are various modifications of the diazo him in this terminology. I consider the term f diazo sulplionate not properly applicable to these products, because the free diazo sulphonic acids are not known. What might be considered the standard method or obtaining diazo sulphonic acids (by acting on a diazo compound with concentrated or sulphuric acid) leads to the formation of complicated bodies oi quite different characteristics. 1 prefer to consider these coinnounds as double uremic-organic salts of sulnhurous acid formed Toy the substitution of one of the sodium atoms or the sodium sulphite by diazo compound. I shall therefore employ the term diazo sulnhite for these products, but I wish to point out that I use this term not as defining any particular structural configuration oi the compound, but rather to indicate the product obtained from a diazo compound by the action or neutral sulphites such as sodium sulnhite in cold neutral or alkaline solution.

In my opinion the goeculiar properties displayed by diazo sulnhites are due to the desmotropic or tautonieric character of sulphurous acid. It has been shown that sulphurou's acid may emt in two structural forms, the. one etricai and the other unsymmetrical. My explanation is that the diazo sulphites formed are themselves deslnotropic and capable of existing in two isomeric structural forms, one the syn lorni and the other the anti form. The syn-diaeo sulphite is first (2) 0 N N Rearrangement 0 In absence of strong anti-diam benzene chloride mentor .and only loses property after a short interval oi time, and also explains whydiazo sulphites show this peculiar property and salts of simple acids, suchas diazo chlorides, do not.

For the purpose or" illustration, 1 shall show the reactions which may be presumed to take place between benzene diazo chloride and sodium sulphite. 'l'l'iese reactions may be shown graphically according to either the diazonium salt theory of Hantsch, or the more modern theory of the ouinonoid configuration of diazo compounds. I

believe that the quinonoid theory fits the lmown facts regarding the properties of disco compounds hotter than the diazonium salt theory, but for the purpose oi comparison, I can showing the essential reactions below in accordance with both theories.

Qcincnold theory sodium chloride sodium sulp cctinic light Sodium enti-diazo benzene sulphite N-ONa Strong ectinic light Diczzmium colt theory sodium diazp benzene sul) pinto (syn-(haze compound ONa N actm c light sodium diazonium benzene sulphito (anti-diazo compound) 0Ne N-ONa 5 N I \0 III Strong actimc light so +1!r (under suitable con- 2 ditions) sodium diazo'benzene hydroxide (syn-diam c mnound) Reaction (1) according to each theory indicates the temporary formation of the reactive and unstable syn-diazo compound. Reaction (2) shows the rearrangement of this compound into the isomeric anti-diazo compound, which is stable in the absence of strong actinic light. It should be noted that the asymmetrical group V properties, while the synmietrical isomeric group in Reaction (2) is negative and displays acid properties. These reactions thus agree with the well-known conversion of anti-diazo compounds into syn-diazo compounds by transfer from an acid to an alkaline medium. It willbe understood that Reaction (3) in each case ismerely symbolical, and will not take place except under suitable conditions, such as the presence of reagents as discussed below.

The correctness of the foregoing theory is evidenced by my discovery that diazo selenites disdated April 23, 1929.

play the same properties as diazo sulphites.

. Selenous acid, like sulphurous acid, is a desmotropic acid capable of existing in two isomeric forms, one symmetrical and-the other unsymmetrical. In fact, I have discovered that diazo selenites possess the advantage over diazo sulphites of being in general more sensitive'to light,

' and one of the features of .my invention resides broadly in the use of diazo selenites in diazo photo-printing. Tellurous acid likewise displays the same properties, but its salts are too expensive for ordinary commercial use.

Although I do not wish to be limited to thetheory just described, I am sufl'iciently persuaded of its accuracy that, for the sake of convenience, I shall designate the non-reactive diazo sulphites and diazo selenites and like compounds existing in the absence of strong actinic light as desmotropic anti-diazo compounds. The term diazo as used herein is usually intended to include tetrazo and polyazo compounds as well as diazo compounds in the strict sense. It will be understood that the reactive isomers of these desmotropic anti-diazo compounds are unstable and can exist for only a short period of time, being decomposed entirely almost as rapidly as formed under the conditions of my diazo photo-printing process.

Both Feer and Lumiere were interested solely in color photography. Feer disclosed only a few azo dyes capable of being formed by diazo photoprinting, and Lumiere, while he extended the field somewhat, directed his eflorts principally toward obtaining azo dyes capable of use in color photography'to give the three primary. colors, blue, yellow and red.

Langguth and Hummel appear to have attempted some work in color .photography along .the lines indicated by Fear and Lumiere, as evidenced by their German Patent No. 465,413

. published September 19, 1928, and the corresponding United States PatentNo. 1,710,455, Langguth and Hummel followed the erroneous nomenclature of Feer and Lumiere.

All ofthese workers were interested only in color photography, and so. far as I am aware, this reaction has not been employed outside .of that the desired direction.

then exposed in moist condition, the degree of field. The processes of these workers do not appear to have progressed beyond the laboratory stage and are not sufllciently developed to be applicable ,to the photo-printingv of, colored designs in competition with known methods of mechanical printing on vegetable oranimal fiber fabrics.

The principal object of my invention is to provide a convenient, practical process of diazo photo-printing applicable to the commercial production of colored designs on any carrier of organic origin;

Both Feer and Lumiere dry-their sensitive paper before exposing to the light. I have discovered that the action of the light is much more rapid andcomplete in the presence of water, and

' may be further expedited by the use ofa reagent capable of taking sulphur dioxide out of the reaction. Such a reagent may be termed a chem-.

ical sensitizer. Furthermore, the amount of water used must be, for best results, within very definite limits, as will be pointedout hereinafter.

The Langguth et al. patents mentioned above disclose the exposure of the sensitive paper in a moist condition, but no instructions are given as to the limits of the moisture nor is anyreason for its use mentioned, nor are any other reagents employed. One of the features of my invention, therefore, is the employment of water in definite proportions, either withor without the addition of a chemical sensitizer as above defined.

Other objects and advantages of my invention will be apparent from the following description of my invention and from the appended claims.

In carrying out my process, I preferably impregnatea carrier, for example paper or cloth,

with a water solution of a desmotropic antidiazo compound and an azo dye-forming coupling component, the diazo compound being incapable of coupling withthe azo component, but generating under the; action of strong actinic light a syn-diazo compound capable of so doing. I preferably incorporate a chemical sensitizer such as one of the reagents mentioned below in the sensitive mixture in addition to the water inorder to insure the completion of the reaction in The sensitized carrier is moisture being carefully regulated as herein after disclosed, to the action of light under; a suitable negative, tracing or other translucent pattern, whereupon an portions of the. carrier exposed to the action of light. I then fix the dye on the carrier, if necessary, and remove theunexposed light-sensitive mixture by washing, preferably with hot water. The carrier is then dried and is ready for use, or, if desired, a further design may be superazo dye isformed on the imposed upon the design already formed by repeating a similar series of steps. 7 v

It will be observed that th foregoing process results in the direct formation of the azo dye on the exposure to light. This may thereforebe called direct diazo photo-printing. It is also possible to carry out my process of diaz'o photo- I printing in an indirect manner. In order to do so, the carrier is coated with the light-sensitive desmotropic antirdiazo compound alone, then exposed to light, and subsequently treated with the coupling component. This may be termed the indirect method, since the dyestuflf is not produced directly upon the exposure but bysubsequent development. The, indirect method of diazo photo-printing has a disadvantage of giving only a weak impression or .thin coating of thedye, for reasons which will be made apparent hereinafter, and in practice requires a white background. -The indirect; method, therefore, has little practical value for obtaining a strong color as compared with mechanical methods of printing. in carrying out my process, therefore, I prefer to utilize the direct method of diazo photo-printing, except where pale shades are desired.

My process is generally applicable to the formation by photo-printing of any azo dye capable oi being formed by the coupling oi a diazo compound and an azo dye-forming component, and possessing the following characteristics:

1. The diazo compound component of the dye must be capable of forming desinotropic compounds having two isomeric forms with desmotropic acids, such as sulphurous and selenous acids. With certain easily identified exceptions, practically any soluble diazo compound can be converted into a desmotropic diazo sulphite or selenite.

2. The desmotropic diazo compound must be light-sensitive, that is to say, it must be converted by the action of light from the anti iorrn incapable of reacting a coupling component into the syn isomer capable either of so doing or of being converted into a syn-diazo compound capable of so doing. Not all diazo compounds or".

desmotropic acids meet this condition, for example, the diazo compounds oi hydrocyanic acid are either not sufdciently light-sensitive, or the two isomeric forms do not have suficiently pronounced acid and alkaline characteristics to provoke the corresponding change of nitrogen valence inchanging anti-diazo compound to syndiazo compound.

3. The solubility of the dye must be less than the solubility of the components from which it is: formed, except in the case of soluble dyes which readily combine with the material of the carrier to produce a new insoluble compound.

My process can be used to apply any azo dye possessing the foregoing qualifications, whether it be acid, basic, or neutral, and whether it be a direct or substantive dye, or a mordant oradjective dye. 'Ihe characteristics of the dye, however, determine the treatment necessary to fix the dye on the carrier and its applicability tedifierent liinds of fabrics. With cotton fabric and direct or substantive dyes insoluble in hot water, no fixing is necessary. With other dyes, the dye should be fixed on the cotton fabric before washing the fabric with hot water to re-,

move the undecomposed sensitive mixture after exposure to the light. In general, it may be stated that the fixing treatment may be the same as would ordinarily be used in dyeing with the same azo dye on a carrier of the same type.

The speed of formation of the azo dyes in diazo photo-printing depends upon (1) the chemical nature of the components, (2) the relative $01117.

bility of the components to the solubility of the azo dye, (3) the sensitivity of the components to light, (4) the presence of water in the sensitive mixture, (5) the use of chemical sensitizers in the sensitive mixture, (d) the quality of the printing light, and (7) the temperature at which the reaction is conducted. f

Factors one and two above depend, of course, upon the particular dye that it is desired to form,

' the selection of the dye being governed by the color desired, the nature of the carrier, and the special requirements of the dyed article, such as fastness to light, and so forth. For a given dye, therefore, these factors are fixed. Where a choice accuser is'tc be made between certain dyes, however, in general, more satisfactory results will be obtained, the more readily the dye flxes upon the fabric to be dyed and the more insoluble the dye as compared to the solubility of the components. The chemical nature of the components determines the character of the formed dye as to whether it is acid, basic or neutral, and hence determines the ability of the dye to fix on the particular fabric to be dyed. in general, the more readily the dye fixes on the fabric, the more completely it will be taken out or" the reaction and hence the more rapid the reaction will be. Likewise, the more insoluble the dye, the more quickly it will be taken out of reaction and consequently the speed of the reaction in the direction oi" forming the dye will be increased.

Factor three, the sensitivity of the components to light, is, of course, dependent largely upon the chemical nature of the components. To some extent, however, it depends upon the nature of the desmotropic anti-diazo compound, that is to say, whether a diazo sulphite or diazo selenite is employed. It is preferable, of course, to employ the more sensitive form of the diazo compound. Factor four, the presence of water in the sensitive mixture, determines to a great extent both the speed and the completeness of the formation of azo dyes in diazo photo-printing. There are a few coupling components, such as naphthylamiue, which will form azo dyes by reaction with diazo sulphites when exposed to strong actinic light in a dry condition. Generally speaking, however, sensitive mixtures containing coupling components and diazo sulphites are decomposed by light only very slowly in the dry condition, thus rendering the use of such dry mixtures impracticable commercially. The preslight more rapid, but renders the formation of the dye more complete. If a sensitized fabric contains less than about 50% of its weight of water, the formation of the dye will not be complete. But an excess of water is also detrimental, because water is to some extent at least a solvent for the dye formed, and the capillarity of the fibers of the fabric tends to spread the dissolved dye, thereby staining parts of the fabric which were not exposed to the light. The best results are obtained when the sensitized fabric during exposure contains from 65% to 125% oiwater by weight based on the weight of the dry fabric.

Just as water aids the sensitivity of the mixture, dehydrating agents destroy its sensitivity. The presence of such materials as alcohol, calcium chloride and acids in the sensitive mixture should be carefully avoided.

When diazo sulphites in Water solution are exposed to the action of strong actinic light, the reaction may be presumed to take place in two stages as indicated below:

(l) 'ONa actions t) and (5) may be enhancedby the removal of the sodium hydrogen sulphite from the zone of reaction. By-so doing, the completeness of the reactions in the direction of forming the 5 hydroxide, in turn,

diazo hydroxide is encouraged, and the disco readily couples with the coupling component to form the azo dye. Further- V more,'the prompt removal of sodium hydrogen sulphite from the reaction zone avoids the possiare many and varied in character, among them being acetone, sodium stannate, sodium aluminate, soap, tri-basic sodium phosphate and borax. I shall designate all such substances as chemical sensitizers, since they do not enter into the main reaction, that is, the formation of the azo dye, but simply speed this reaction by the removal of sulphur-dioxide or its compounds. The term 25 sensitizer as used in this specification and the appended claims should, therefore, be understood as meaning a substance possessing this property of removing sulphur dioxide under the required conditions. Obviously, the sensitizer must be one which has no deleterious effect on the azodye or its components.

The sensitizers mentioned act in difierent ways. Acetone forms an addition product with, sodium hydrogen sulphite, thus withdrawing the latter 5 from the reaction; The aldehydesand many other ketones resemble acetone in possessing this property, but acetone is particularly useful be-, cause it is relatively inexpensive, an excellent solvent for organic substances and miscible with water inany proportion. The inflammability of' acetone is the only drawback to its extensive use. These addition products are known as bisulphite compounds. i

Sodium stannate is a very energetic -sensitizer, and even permits diazo sulphites to be decomposed by strong actinic light in the absence of a coupling component. Sodium aluminate is less important and may be-used only with amines. Soap is a useful sensitizer when the fixingof the dye requires a weak alkaline medium. Its use has the disadvantage of producing a slight coloring on the unexposed portions of the fabric.

The salts of weak, non-volatile inorganic acids and strong bases, such as tri-basic sodium phos-' phate and borax, when used as sensitizers readily combine with sulphurous acid or hydrogen sulphite'to form neutral fsulphites, and can frequently be used to better advantage than soap. Free alkali could, of course, be used to accomplish the same result, but might have a disad- ,vantageous eflect upon the dye or the carrier.

The quality of the printing light, factor six above, has 9, good deal to do with the speed of the reaction. The initial velocity or the photochemical reaction isdetermined by the light absorbing ability of the components of thesensitive. mixture. ,The light absorption of the sensitive mixture, which is generally of yellow or brownish-yellow color, is chieflyin the blue, violet and ultra-violet parts of the spectrum The printing light should therefore be rich in light of this'character, that is to say, it should be strongly actinic. I have found that if the formed dye absorbs considerable light during the re-' action, this absorption of light by the formed 5 dye increases the speed of the reaction. This may be due either to the additional light energy thus made available in the reaction zone for the photo-chemical reaction, or merely to an increase of temperature in the reaction zone. Whatever the cause, the fact is that the best results are obtained when light absorption by the formed dye is encouraged. The light absorption of the formed dye depends upon its color and may be in any part of the spectrum. The source of printing light should therefore radiate all rays from ultra-violet to infra-red.

From the foregoing it will be apparent that light filters are not only unnecessary but undesirable, and that the sensitized fabric should be subjected to the direct action of the printing light, except for such interference as is inten-v tionally provided by the negative or other pattern. The use of a light filter greatly increases the time required for exposure, since it reduces the light absorption both by the components of the sensitive mixture and by the formed dye, and particularly because it cuts out the. infra-red rays and their attendant heat energy. v

Therichness of the printing light in 'ultraviolet-and infra-red-rays has a decided effect upon the time of exposure. Using a low pressure mercury vapor lamp, with an intensity of illumination of 100 candle-feet per square foot,

the exposure required may vary from one to five" minutes. Using a high pressuremer'cury vapor lamp or an open carbon arc lamp with so-called ultra-violet carbons, with the same intensity of illumination, the time of exposure required is only about one-quarter as long.- The latter sources of light require a shorter time because of their richness in ultra-violet and infra-red rays. 1

The efiect of the reaction temperature, factor seven above, on the speed of formation of the azo dyes has already been mentioned in connection with the absorption of light. I have found that increased temperature favors the formation of the azo dye, provided, -of course, that the temperature does not exceed the temperature of decomposition of the components of the sensitive mixture, say 100 C. v I have also found that the rise in temperature of the fabric during ordinary periods of exposure is not sufliciently great to use decomposition of the components of the In the preferred embodiment of my invention,

therefore, I expose the sensitized fabric in a warm tive mixture. It is therefore neither nec-' essary nor desirable to use cooling frames during condition to the direct action of strong actinic light, siich as that provided we high pressure mercury vapor lamp as described above, the negative, of course, being placed between the lamp and the fabric.

My complete process of dish) photo-printing comprises the following steps: (1) Preparing a solution of the desired lightsensitive desmotropic anti-diazo' compound;

(2) Preparing a solution of the desired couplin component; Q

' (3) Preparing the sensitive mixture;

(4). Impregnating the fabric with the sensitive mixture; 1

(5) Regulating the moisture content of the fabric to secure the proper degreeof humidity;

(6) Exposing the fabricto'strong aotinic light under a negative;

azo dye requires the addition of (7) Fimng the formed dye on the fabric if necessary;

(8) Washing the fabric;

(9) Drying the fabric.

The general method advanced by Lumiere and described above mayadvantageously be used for preparing the light-sensitive desmotropic antidiazo compound to be used in making up Solution I. The choice of the particular diazo compound from which one prepares the desmotropic anti-diazo compound depends upon the particular azo dye which it is desired to form on the fabric; Ordinarily, I convert the diazo compound into either a sulphite or a selenit'e, but mixturesof the two may be employed if desired. I have found that a convenient strength of solutions of diazo compound is 5 centigram-molecules in 1000 c. c.- of water for tetrazo sulphites or selenites, and 10 centigram-molecules in 1000 c. c. of water for diazo sulphites or selenites. These compounds when dissolved in water and kept in tightly corked bottles are very stable and do not decompose under ordinary temperature and light conditions for at least six months. Some such solutions have shown no marked decomposition after standing for a year.

The coupling component to be used also depends upon the azo dye to be formed. The method of preparation of such coupling components is no part of my invention and is well known, and hence need not be described herein. The quantity of the coupling component in the sensitive mixture should preferably be either just sumcient or slightly less than enough to combine with the desmotropic' anti-diazo compound present. An excess of the coupling component should be avoided, as should also too great concentration of the coupling component in the sensitive mixture. With too great concentrations of some coupling components, the unexposed parts of the design may be tarnished by a combination of the coupling component with thefabric being dyed. Coupling components so combined with the fibers of the fabric are sometimes very dimcult-to remove by washing. I have found a concentration of the coupling component in the sensitive mixture of four centigram-molecules in 1000 c. c. of water to be convenient and practical. It is-of great importance to use freshly prepared solutions of coupling components, inasmuch as many coupling components are susceptible to hydrolysis and a few to photolysis.

The sensitive mixturemay be made up by mixing appropriate volumes of the solutions of the desmotropic anti-diazo compound and of the coupling component. The density of the color obtained depends to a certain extent upon the concentration of the sensitive mixture; the more concentrated the sensitive mixture the deeper the color. It is usually inadvisable, however, to increase the concentration of the sensitive mixture materially above the limits mentioned above. In many instances deep colors may be obtained readily by the addition of salting-out. agents, such as sodium sulphate and sodium chloride, to the sensitive mixture. The addition of salting-out agents is especially to be recommended when the dyeing of the fabric with the corresponding such agents.

. The sensitive mixture may be completed by the addition of a sensitizer as described above. The choice of the sensitizer likewise depends upon the dye to be formed, some of the sensitizers mentioned giving better results withsome dyes than with others. The more important conditions eanne? regulating the choice of the sensitiser have been outlined above. The sensitizer may be added to the combined solutions of the desmotropic antidiaao compound to either of these solutions before mixing.

Ihe impregnation of therabric with the'sensi tive mixture may be accomplished simply by dipping the fabric in the sensi ive mixture. The excess sensitive mixture is then removed by wringing or pressing.

I have already pointed out the desirability of having the amount of water in the fabric within definite The regulation of the percentage of moisture in the fabric may readily be accomplished by placing the fabric in a closed steam chamber full of saturated steam. The temperature of the chamber is and the coupling component, or.

then regulated to produce 7 humidity conditions corresponding to the desired percentage of water in the fabric. A condition will very quickly be reached in which the amount of water in the fabric is in equilibrium with the the fabric may then steam in the chamber, and he removed. In most cases, the temperature should not be over 100 63., because at this temperature some of the components begin to decompose.

The exposure may be performed in the ordinary manner of making blue prints and the like, the

sensitized fabric being placed in a printing frame under a negative or other pattern bearing the desired design. The use of a reflecting surface beneath the fabric considerably decreases the re-= quired time'of exposure. For large scale commercial operations, special printing machines are necessary, but such machinery forms no part of the process invention herein described. As pointed out above, it is neither necessary nor olesirable to use light filters or cooling frames during the exposure. i 7

As has also been pointed out above, the sensitized fabric should preferably be warm during the exposure. more the humidity of the fabric has been regulated in a steam chamber as described above, the fabric may simply be placed in the printing frame before it has had an opportonity to cool greatly. In some cases, itmay be desirable to provide the printing frame with heating means, which may take any conventional form. The temperature of the fabric at may advantageously be the instant of exposure beinveen 30 C. and C. ture probably takes place but will be only beneficial,

Some rise in temperaduring the exposure, since during the short exposures mentioned; the temperature cannot I rise as far as the decomposition temperature of the components.

Whether or not it is necessary to fix the dye with hot water at a. temperature of 51.- to. 80 C.

The washing is continued until all or substantially all of the sensitive mixture is eliminated. Acetic acid, sodium acetate or soap may be'added to the wash Water cases where they are etfective in removing the undec'omposed sensitive mixture and do not affect the dye. The final rinsing of the fabric should bewith cold water.

The drying of the fabric may be accomplished EXAM1 LE ADYEING wrrn Fmwazms tin uous stirring,

' sample of thesolution with an alkaline solution of in the manner ordinarily employed in dye plants.

Steps 4, '7, 8 and 9 as outlined above may be per,- formed in regular dyeing machines.

The final product of the process just is a dyed fabric having all of the properties of any fabric dyed with the same azo dye in the ordinary manner. The dyed fabric may therefore be subjected to any after treatment capable of being used in connection with that azo dye in ordinary dyeing operations. These after treatments include: (1) treatments with metallic salts, such as salts of copper, chromium and barimm; (2). coupling with diazo compounds followed by the usual development; (3) formation of polyazo dyes by diazotizing the dye already obtained on the fabric followed by development with the proper developer; (4) topping the azo dye withaniline dyes.

In general, in diazo photo-printing all of the rules for the treatment of the azo dye under consideration are to be strictly followed. Thus, the rules for fixing and after treatment, the use of salting-out agents, and so forth, all follow the corresponding rules for ordinary azo dyeing.

Where multi-color printing is to be employed, any after treatments to be applied to the printed dye should be carried out before applying any subsequent dye to the fabric, since these treatments increase the fastness of the dye originally printed. I I

The following specific examples are illustrative of the way in which my invention may be applied. It is to be understood, however, that the specific examples given are merely by way of illustration, and that my process is by no means limited to the application of the specific azo dyes mentioned in these examples:

YELLOW L Step 1.--Prepdring a solution of the light-sensitine desmotropic anti-diazo compound Dissolve 9.3 grams of aniline in 10 c. c. of hydrochloric acid (specific gravity 1.18). Add 100 c. c. of water and 50 grams of crushed ice to the resulting solution of aniline chloride.

Dissolve '7 grams of sodium nitrite in 50 c. c. of water and add 50 grams of crushed ice. Pour 10 c. c. of hydrochloric acid (specific gravity 1.18) into the solution of sodium nitrite. Add another 50 grams of crushed ice. Stir the resulting solution of nitrous acid until it reaches a temperature of about 8 C.

Add the cool solution of anilinechloride gradually to the nitrous acid solution with continuous stirring. Allow the resulting diazo benzene solution to stand for about fifteen minutes.

Dissolve 25.2 grams of anhydrous sodium sulphit'e (or 26.8 grams of anhydrous sodium selenite) in 100 c. c. of water. Cool about 10 C. by the addition of 50 grams of crushed ,ice; r Y I The diazobenzene solution prepared as described above isslowly added to the sodium sul phite (or sodium selenite) solution with con- After twenty minutes, test a a phenol; or a naphthol.- characteristic diazo reaction, sulphite '(or selenite) solution,

If the test shows the add more sodium until a repetition of the test shows no diazo reaction.-

-- Then dilute the solution with water to a volume of 10000.0. I r is 10 centigram-molecules of benzene diazo sulphite (or selenite) in 1000 c. c. of water.

described twenty minutes. 7

.pressed fabric may be placed in a closed steam the solution to The concentration of this solution Step 2.--Preparing a. solution of the coupling component Dissolve 27.5 grams of l-p-sulpho-phenyl-Iimethyl--pyrazolon in 100 c.-c. of a4% solution of sodium hydroxide. The concentration of this solution is centigram-molecules in 100 c. c. of water.

Step 3.--Preparing the sensitive mixture Mix 10 parts by volume of the benzene diazo sulphite (or selenite) solution with one part by volume of the pyrazolon solution, preparing only enough of the sensitive mixture to meet immediate requirements. a,

Step 4.--I1'npregnating the fabric with the sensi- I tine mixture The piece of wool, silk or cotton to be dyed (previously thoroughly washed to remove grease, oil and dirt) is dipped in the sensitive solution and saturated therewith. The piece of fabric is then gently pressed to remove the excess sensitive mixture.

Step 5.-,-Regulating the moisture content .of the fabric to secure the proper degree of humidity The fabric may be allowed to dry in an open room at ordinary room temperature for about For more exact results, the

chamber filled with saturated steam at a suitable temperature, say 85 0., and the temperature raised a few degrees. The fabric may be removed after, say a quarter of an hour, the time not being important as the equilibrium condition is quickly reached and thereafter the moisture content of the fabricdoes not change. 4

Step 6.Ea:posing the fabric to strong actinic light under .a negative The moist fabric is placed in a printing frame under a negative and exposed to strong actinic light from a 120 volt high pressure mercury vapor lamp at a distance of 18 inches for a few seconds. The time of exposure under the negative depends,

of course, on the density of the negative. The P time given is for a negative having clear transparent parts and dense opaque parts. Using a low pressure mercury vapor lamp at the same distance, the time required would be from two to three minutes, and for a 150 watt nitrogen filled tungsten filament lamp the time required would be five to ten minutes.

Step 7.--Fi.ring the formed dye on the fabric With silk and wool fabrics, no fixing treatment is necessary prior. to washing. For cotton fabrics, the fabric should be washed in a 10% solution of barium chloride in water. This barium chloride treatment converts the-formed dye into an insoluble colloidal lac, which is very fast to light. This fixing treatment may advantageously be employed even for silk and woolen fabrics." I

Step 8.-W ashing the fabr c The fabric is then thoroughly washed with hot water at a temperature of from to 80 C. for ,ten to f lfteen minutes to remove all of the unexposed sensitive mixture. It is preferable to acidity the water slightly with hydrochloric or acetic acidi Step 9.-- Drying the fabric manner. I

j in 1000 c. c. of water.

The design thus formed on the fabric is of a yellow color, and the formed dye is known as fiavazine yellow L. I

EXAMPLE BDYEING wrrrr CONGO 4R (RED) Step 1 Prepare a solution of ditolyl tetrazo-sulphite having a concentration of 5 centigram-molecules This solution may be prepared from 21.2 grams of commercial tolidine in the manner given in the preceding example for the preparation of benzene diazo sulphite from aniline.

Step 2 Dissolve 2.45 grams (1 centigram-molecule) of sodium naphthionate in c. c. of water, separately dissolve 1.54 grams (1 centigram-molecule) of sodium resorcinate in 10 c. c. of water, and then mix the two solutionstogether.

Step 3 Mix 200 c. c. of the ditolyl tetrazo-sulphite solution and 50 c. c. of the coupling component solution, and dissolve 2.12 grams of sodium stannate in the resulting sensitive mixture.

Steps 4, 5 and 6 These steps may be performed as in Example A, except that the exposure should be somewhat longer. For example, using a low pressure mercury vapor lamp at a distance of 18 inches, the exposure should be from t to 5 minutes.

Steps 7 and 8 I No special fixing treatment is required if the silk, wool or cotton fabric is washed with hot water as described under 8 in Example A. A

very fast brownish red color may, however, be

obtained by treatment with a solution of diazop-nitro-benzol before washing, and then washing with cold water.

Step 9 As in Example A. EXAMPLE C-DYEING WITH OXAMINE BLUE 4R Step 1 Prepare a solution of ditolyl tretrazo-sulphite having a concentration of 5 centigramvmolecules in 1000 c. c. of water as specified in Example B.

Step 2 Dissolve 2.63 grams (1 centigram-molecule) of sodium 2-amido-5-naphth l-7-su1phonate and 2,5 grams (1 centigram-molecul'e) of sodiuml-naph- Step 3 Mix 200 c. e. of the Steps 4, 5 and 6 These steps should be performed as in Example A.

Step 7 The dye should be diazotized on the fabric in the usual way, using nitrous acid solution, and should then be developed with alkaline beta.-

naphthol solution. This gives a very fast deep blue color. I

Steps 8 and 9 Same as in Example A.

EXAMPLE BDYEING VVITH'DIAMINE BoRnnAU Step 1.

Prepare a solution of dianisol tetrazosulphite having a concentration of 5 centigram molecules in 1000 c. c. of water. This solution may be prepared from 24.4 grams of dianisidine in the manner given in Example A for the preparation of benzene diazo sulphite from aniline.

Step 2.-

Dissolve 2.44 grams of meta-toluylendiamine in 100 c. c. of hot water at a temperature of ill Step 3.

Pour 200 c. c. of the dianisol tetrazo-sulphite solution into the 100 c. c. of the coupling component solution. If the liquid is not transparent and clear, it should be heated until all of the components are dissolved. Add l5 0. c. of acetone.

Steps 4, 5 and 6. These steps may be performed as in Example A.

Step 7..

Steps 8 and 9.

- These steps may be performed as in Example A.

The term pattern as used in the appended claims is intended to include any pattern or design having transparent or translucent parts, whether a photographic negative, tracing, stencil, or any other medium capable of modifying or regulating the exposure of the carrier to light.

It will be apparent to those skilled in the art that my process may be modified in many particulars without departing from the, spirit of my invention, and I desire to be limited, therefore, only by the scope of the appended claims.

I claim: 1. The process of diazo photo-printing which comprisespreparing a water solution of a lightsensitive desmotropic anti-diazo compound and an azo dye-forming coupling component, im-

pregnating a carrier with the said solution, ex-

posing the carrier while containing at least 50% of water by weight of the dry carrier to the action of actinic light under a pattern, removing the undecomposed sensitive mixture, and drying the carrier.

' 2. The process as claimed in claim 1 in which the water content of the carrier during exposure is between 65% and 125% by weight of the dry carrier.

3. The process as claimed in claim 1 in which the actinic light contains all rays from ultraviolet to infra-red.

4. The process as claimed in claim 1 in which the moist carrier is at a temperature of at least 30 C. at the commencement of the exposure.

5. The process of diazo photo-printing which comprises preparing a sensitive mixture containmay be diazoti'zed' ing water, a light-sensitive 'diazo compound and an azo dye-forming coupling desmotropic anticomponent, impregnating a carrier with the sensitive nriixture regulating the water content of the carrier betweenthe limits oi 50% 91115112572, by weight of the ,dry carrier, exposing the carrier so moistened o 'theyiaction oi actinic vlight moving the undecoinposed nd the carrier.

' claimei in claim '5 in whichithe light strong actinic light containingalhrays from ultra-violet to infra-red.

' the moistened carrieifis commencement of the exposure; V

9."The process or diazo photoeprinting which comprises preparing a sensitive mixture contain- ;"1:"The processas imed-in claim 5 in which 'ie'i' substantially above room mniencement of the ex- 30' C. ancl'not greatly exceeding fifi 'jiQat "the ing waterfa light-sensitive desinotropic anti-6h azo sulphite, an azo dye-forming coupling com-' ponent and a chemical sensitizer adapted to remove sulphur dioxide from the reaction, impregnating a carrier with the sensitive mixture, exposing the carrier in moist condition to the action of actinic light under a pattern, removing the undecomposed sensitive mixture, and drying the carrier. 9 I 4 10. The process as claimed in claim 9 in which the sensitiz' r is sodium stannate.

11) The process as claimed in claim 9 in which the sensitizer is acetone.

12. The process as cla' edin claim 9 in which 7 the water content of the carrier'during exposure is between 50% and 125% by weight of the dry carrier.

rays irom ultra-violet to inf claimb in whicha at a'jiitemperature above 13. The process as claimed in claim 9 in which the light is a strong actinic light containing all aired;

14. In a. process .of diazdiiiahpto-printing, the steps of impregnating a carrier with a water solution of a light-sensitive anti-diazo compound,

and exposing the carrier to the action of actinic light under a pattern whilecontaining at least 50% of water by weight of'the dry carrier. v

15. In a process of diazo photo-printing, the steps ofjimpregnating .acarrier with a water solutionof a light-sensitive anti-diazo compound, and regulating the water content of the carrier between the limits of 65%and 125% by weight ,of the Carrion. n 16. In a, process of diazo photo-printing, the

step of impregnating a carrier-with a water solution of a light-sensitive desmotropic anti-diazo sulphite and an azo dye-forming coupling component, and forming the dye on themoist carrier by the action of actinic light, the water content of the carrier during exposure to the actinic ligh being between 50% and 125% by weight of the dry carrier.

18. The process of diazo photo-printing comprises sensitizing a carrier with a water solusulphite' and a chemical sensitizeradapted to re;-;

7 move sulphur dioxide from thereaction. 2.0.

17. The process of diazo photo-printing which comprises sensitizing a carrier with a water solution of a light-sensitive desmotropic anti-diazo' tion of a light-sensitive desmotropic anti-diazo v selenite and an azo dye-forming coupling component, and forming the. dye on themoist carrier by the action of actinic light, the water contentof the carrier during exposure to the actinic light being between and-% by weight of the dry carrier.

VLADIMIR C. AKIIEITIEVSKY. 

